The present invention relates to a rubber composition for a tire and a tire having a tread using the same.
In recent years, properties required for tires on automobiles have become diverse including wet skid performance, abrasion resistance, and steering stability other than low fuel efficiency and in order to improve these properties, various devices have been made.
For example, a rubber composition compounded with silica in a styrene-butadiene rubber having a large amount of a styrene content (high styrene SBR) to improve various properties such as wet skid performance and steering stability at high-speed running is known. However, the rubber composition has a problem that grip performance is significantly lowered since rigidity of a rubber is lowered after repeating running. Also, since silica contains silanol groups on its surface, silica particles tend to coagulate each other, and as a result, the compound also has a problem that its processability such as extrusion becomes insufficient due to insufficient dispersion of silica particles into the rubber. In addition, a rubber composition compounded with powders of an inorganic compound together with carbon black or silica in diene rubber is also known. However, the inorganic compound powder is also difficult to disperse into a rubber as is the same as silica, and when particularly used together with silica, the rubber composition may have a problem that wet skid performance is not sufficiently improved
Also, as a method to improve low fuel efficiency of a rubber composition, an example is a process of decreasing an amount of a filler, which is a reinforcing agent, however, rubber hardness is lowered, which causes a problem that steering stability and wet skid performance are deteriorated.
JP-A-2005-213353 discloses a rubber composition having improved processability, low fuel efficiency, and wet skid performance through preparing the rubber composition by a specific process, and a pneumatic tire having a tread using the same. However, effects of improving these properties are not sufficient, and a rubber composition excellent in steering stability is not disclosed.